1. Field of the Invention
The present invention relates generally to the field of tool bits and tool bit chucks, and more specifically to a tool bit including an elongate shaft having a mounting end and a working end, the mounting end preferably being wide relative to the shaft for increased stability and optionally having an axial bore containing a row of loosely fitting stabilizing balls, a flywheel portion extending radially from the shaft, the flywheel portion preferably being a hexagonal cylinder or disk, the working end taking any of several useful shapes, such as a drill cutting edge, a screw driver head, a reamer or a socket engaging end; and also specifically to a mounting chuck for the tool bit having a square bit receiving tube into which the tool bit mounting end is inserted, ports in opposing tube sides for loosely receiving a locking ball, such that these ports align with a groove in the tool bit mounting end so that the locking balls can enter the groove through the ports, a camming tube which slides over the receiving tube, having a camming portion protruding from its inner wall with a central recess into which the locking balls can retreat when the recess aligns with the ports, to release the bit end, the shoulders of the camming portion on either side of the recess serving to force the locking balls to protrude beyond the receiving tube into the groove to lock the mounting end into the chuck, when one of the shoulders aligns with the ports.
2. Description of the Prior Art
There have long been tool bits and chucks for fast, snap-in and snap-out engagement. A problem with these bits and chucks has been that the snap in engagement, often by cammed balls, is not as tight as a clamping key chuck engagement, and the bit often vibrates and wobbles. Other problems have included chuck bulk, complexity, unreliability, and manufacturing expense.
Wienhold, U.S. Pat. No. 4,900,202, issued on Feb. 13, 1990, discloses a snap-in tool bit and a chuck assembly for the tool bit, intended to prevent undesired tool bit extraction from the chuck. The tool bit itself includes a shank portion with a circumferential engagement groove. The chuck includes a spindle having an axial bore for receiving the shank portion of the tool bit, and radial ports opening into the shank receiving bore which contain detent balls. The balls are cammed radially inward to partially enter the engagement groove by a cam shoulder projection within a spring-biased locking sleeve. The wall of each port are curved inward at their inner ends to retain the balls. All illustrated variations of the shoulder projection have at least one additional step or ramp for bearing against the balls and stopping them from rolling within the curved ports. A problem with the Wienhold tool bit is that the ball engagement does not provide the tight clamping of a key chuck, and no provision is made to compensate for this loss of stability. A problem with the Wienhold chuck is that the curved ball ports must have substantial depth. If they do not, the additional step or ramp for jamming the ball against rotation could cause the balls to roll out of their ports. To make the ports deep, the spindle must be made thick and needlessly heavy and costly in materials. The additional step also raises manufacturing costs.
Sheets, U.S. Pat. No. 5,062,749, issued Nov. 5, 1991, teaches a tool bit and tool coupler similar to that of Wienhold. The Sheets tool bit differs from that of Wienhold in that a radial flange on a shank must be provided for proper interaction with the Sheets chuck, adding expense, while only negligibly increasing radial mass distribution and stability. The Sheets chuck differs from Wienhold in that the cam shoulder portion is narrower and no additional cam step is provided. A problem with the Sheets chuck is that the narrowness of the shoulder portion enhances the potential for unwanted release from accidently nudging the sleeve. Sheets also differs from Wienhold in that two or more balls may be contained within each port rather than one. Having additional balls in a port merely makes it necessary for the port to be deeper and the spindle thicker and heavier. The two springs and the two diameter axial bore make Sheets complex and expensive. Another problem with the Sheets chuck is that the sleeve must be pushed away from the user for release of the tool bit. Pushing on part of an appliance while holding the appliance is more awkward and difficult than pulling on the part.
Martindell, U.S. Pat. No. 4,692,073, issued on Sep. 8, 1987, teaches another circumferentially grooved tool bit and cammed ball tool chuck with an outer spring-biased sleeve. Rather than positioning a flat cam shoulder over a ball to lock the ball in the tool bit groove, a taper is provided which merely biases the ball radially inward. A problem with Martindell is that the tool bit groove is also tapered or curved. Pulling axially on the tool bit could thus cause the tapered groove to cam the ball back out of the groove and force the sleeve into an unlocked position. In this way, if a tool bit becomes caught during use, pulling on the chuck could unlock the sleeve and leave the tool bit stuck in the work piece. Another problem with the Martindell chuck is that, like the Sheets chuck, the sleeve must be awkwardly pushed away from the user for release tool bit release.
Falchle, U.S. Pat. No. 3,945,653, issued on Mar. 23, 1976, discloses a chuck for securing a tool bit having a shank with a circumferential groove. The chuck includes a spindle having an axial bore for receiving the tool bit shank. The spindle also has a slot on one side into which a cylindrical locking element is laterally positioned. The slot angles through a wall of the spindle, and a sleeve slidingly fits around the spindle, containing a retaining compartment for holding the ends of the locking element. Sliding the sleeve axially relative to the spindle in one direction causes the sleeve retaining compartment to pull the locking element radially outward along the angled slot. When the element is in an outward position, the tool bit shank is free to slide into and out of the axial bore. Moving the sleeve in the opposite axial direction pushes the element radially inward along the angled slot and, if a tool bit shank is in the bore, into the groove to lock the bit in the chuck. A problem with Falchle is that the spindle must be thick and heavy to contain a slot within which the cylindrical element can thus slide. Also, no provision is made to add stability to the tool bit.
Kouvelis, U.S. Pat. No. 4,818,157, issued on Apr. 4, 1989, teaches a quick-change adaptor and tool bit for use with the adaptor. The tool bit has a multi-sided shank portion with a circumferential groove, for fitting into a tubular portion of the adaptor. The adaptor has a shaft portion for fitting into the chuck of a powered rotary tool coaxially attached to the tubular portion. A spring-loaded detent ball is contained within a radial port in the wall of the tubular portion, so that when a tool bit shank portion is fitted into the tubular portion, the ball snaps into the groove to secure the tool bit. A problem with Kouvelis is that the detent ball is biased rather than locked into the groove, and the resulting tool bit engagement is thus unreliable. Another problem is that Kouvelis does not disclose a chuck for permanent installation on a power tool, but merely a small adaptor for use in an existing chuck. Finally, Kouvelis does not compensate for the potential loss in tool bit stability between the chuck and the adaptor and between the adaptor and the tool bit.
Smith, U.S. Pat. No. 3,734,516, issued on May 22, 1973, teaches a chuck assembly for a tool bit adaptor. As in Kouvelis, a tool bit fits into the adaptor and the adaptor fits into a power tool chuck. A problem with Smith is that the chuck is a multi-spring, complicated assembly which would be expensive to manufacture and likely subject to failure. Another problem is once again that stability is lost at multiple couplings and there is no structure to compensate for this loss.
Ondeck, U.S. Pat. No. 2,809,529, issued on Oct. 15, 1957, discloses a screw driver attachment including a tool shank joined at its mounting end to a disk member. The disk member is contained within a housing, and a roller bears against the disk member. A problem with Ondeck if used as a drill tool bit is that there is no mounting end opposite the shank end which could fit into a chuck.
Seibert, U.S. Pat. No. 3,735,993, issued on May 29, 1973, teaches a self-release and reload tooling device. The device includes an adaptor having a threaded bore for receiving a tool shank and having a threaded external surface for receiving an adaptor nut. A problem with Seibert is that the tool bit is screwed into the bore in the adaptor, so that there is limited stiffness between the adaptor and the tool shank, minimizing stability.
Koster, U.S. Pat. No. 5,116,172, issued on May 26, 1992, discloses a composite rotary cutting tool and adaptor, and a method of making them. A problem with Koster is that the tool shank is secured into the adaptor with an adhesive. Since an adhesive can deform and compress, it offers limited shank stiffness and stability.
Hemmings, U.S. Pat. No. 5,102,271, issued on Apr. 7, 1992 and Stribiak, U.S. Pat. No. 4,811,843, issued on Mar. 14, 1989, both teach collet drill bits having depth limiting rings. A problem with both devices is that the rings or gripping collars are apparently of the conventional type described in Stribiak, which are slidably fitted onto the tool shank and are of lighter and softer material than the shank. A light material such as plastic cannot serve as an effective flywheel and the sliding fit does not produce the solid, unified structure important to stability.
Saxton, U.S. Pat. No. 4,536,108, issued on Aug. 20, 1985, discloses a flexible micro-drill bit. Saxton includes a standard, circular mounting end and a reduced-diameter midsection leading to a narrow drill shank for fine work. A problem with Saxton is that it fails to teach a flywheel portion larger than the conventional chuck receiving opening. As a result, any stabilizing effect of the larger mounting end, particularly with a standard size shank, is both very minimal and accidental.
Clark, U.S. Pat. No. 2,718,806, issued on Sep. 27, 1955, reveals a magnetic driving tool having a multi-sided shank and a socket-receiving end structure. Sockets snap over a spring-loaded ball at the outer end of the receiving end structure and against an expanded stop portion. A problem with Clark is that the mounting end of the shank is apparently of conventional chuck opening diameter and thus provides no increased stability.
Schroer, U.S. Pat. No. 20,498, dated Sep. 28, 1898, appears to teach a reamer having a mounting end of smaller diameter than the tool shank itself. This size relationship actually leads to a reduction in stability. An expanded portion is provided, but is only negligibly larger than the tool shank, and thus would have a negligible effect on stability. The expanded portion is apparently intended as a stop rather than as a stabilizer.
It is thus an object of the present invention to provide a tool bit and chuck which permit fast coupling and uncoupling of the tool bit.
It is another object of the present invention to provide such a tool bit and chuck which stabilize the tool bit for smooth operation with minimal vibration.
It is still another object of the present invention to provide such a chuck which has a cammed release sleeve operated by pulling the sleeve toward the appliance on which the chuck is mounted.
It is finally an object of the present invention to provide such a tool bit and chuck which are durable, reliable and relatively inexpensive to manufacture.